title: β-Xenophyllite-type Na4Li0.62Co5.67Al0.71(AsO4)6.
abstract: The title compound, tetrasodium lithium cobalt aluminium hexa-(orthoarsenate), was synthesized by a solid state reaction route. In the crystal structure, Co(2+) ions are partially substituted by Al(3+) in an octa-hedral environment [M1 with site symmetry 2/m; occupancy ratio Co:Al = 0.286 (10):0.714 (10)]. The charge compensation is ensured by Li(+) cations sharing a tetra-hedral site with Co(2+) ions [M2 with site symmetry 2; occupancy ratio Co:Li = 0.690 (5):0.310 (5)]. The anionic unit is formed by two octa-hedra and three tetra-hedra linked only by corners. The CoM1M2As2O19 units associate to an open three-dimensional framework containing tunnels propagating along the a-axis direction. One Na(+) cation is located in the periphery of the tunnels while the other two are situated in the centres: all Na(+) cations exhibit half-occupancy. The structure of the studied material is compared with those of various related minerals reported in the literature.
authors.affiliation: Laboratoire de Matériaux et Cristallochimie, Faculté des Sciences de Tunis, Université de Tunis ElManar, 2092 Manar II Tunis, Tunisia.
authors.forename: Riadh
authors.initials: R
authors.lastname: Marzouki
authors.forename: Wafa
authors.initials: W
authors.lastname: Frigui
authors.forename: Abderrahmen
authors.initials: A
authors.lastname: Guesmi
authors.forename: Mohamed Faouzi
authors.initials: MF
authors.lastname: Zid
authors.forename: Ahmed
authors.initials: A
authors.lastname: Driss